The construction of a hot water heater consists essentially of an inner tank which constitutes a reservoir in which water is heated. The inner tank is insulated from an outer casing by spacing an outer casing from the inner tank and filling the interstices with an insulating foam or fibreglass material. The top of the tank is provided with conduits to admit water into the tank and to remove hot water from the tank. These conduits are usually interconnected to the cover of the outer casing through an interconnecting nipple and bushing. Usually, copper piping is connected to the outer end of the nipples. The nipples are secured to the top wall of the outer metal casing by metal bushings.
It has been found that an important amount of heat is lost through the outer casing top wall due to its contact with these nipples. The nipple is a metal tube which is highly thermally conductive as well as its couplings. Accordingly, heat exchange between the nipple is made with the top wall of the outer casing which is also constructed of metal. This heat is propagated throughout the top wall of the casing and into the other nipple and the tubes and the metal conduits secured thereto. Holes are presently punched in the top wall of the outer casing and are about 1316 inch less than the OD of the nipples. These holes are also not always concentric with the nipple OD.
There is a requirement to render hot water heaters thermally efficient and this is done by isolating the inner tank from the outer casing all about the tank. Such inner tanks, and the ones which are heated by electrical resistive heating elements, are mounted on foam bases whereby the tank is well isolated at the base and all around. However, in order to render the tank more efficient, we have discovered that there is a need to insulate these nipples to substantially reduce the heat loss which is transmitted through the top wall of the outer casing.